Abstract
Members of the Omp85/TpsB protein superfamily are ubiquitously distributed in Gram-negative bacteria, and function in protein translocation (e.g., FhaC) or the assembly of outer membrane proteins (e.g., BamA). Several recent findings are suggestive of a further level of variation in the superfamily, including the identification of the novel membrane protein assembly factor TamA and protein translocase PlpD. To investigate the diversity and the causal evolutionary events, we undertook a comprehensive comparative sequence analysis of the Omp85/TpsB proteins. A total of 10 protein subfamilies were apparent, distinguished in their domain structure and sequence signatures. In addition to the proteins FhaC, BamA, and TamA, for which structural and functional information is available, are families of proteins with so far undescribed domain architectures linked to the Omp85 β-barrel domain. This study brings a classification structure to a dynamic protein superfamily of high interest given its essential function for Gram-negative bacteria as well as its diverse domain architecture, and we discuss several scenarios of putative functions of these so far undescribed proteins.
Highlights
The Omp85/TpsB protein superfamily is a unique group of bacterial outer membrane proteins, which can function as protein translocases or as membrane protein assembly factors (Mazar and Cotter, 2007; Hagan et al, 2011); with a well-studied example described for each of these two functions: The TpsB family protein FhaC secretes a partner protein (FHA) through the outer membrane to the extracellular milieu (Mazar and Cotter, 2007; Jacob-Dubuisson et al, 2013)
The protein architecture and sequence signatures identified within the Omp85/TpsB superfamily enables a classification structure to this highly diverse group of proteins
It suggests that the complex process of assembling proteins into bacterial outer membranes selects for diversity in the genes encoding BamA paralogs and BamA-related functions
Summary
The Omp85/TpsB protein superfamily is a unique group of bacterial outer membrane proteins, which can function as protein translocases or as membrane protein assembly factors (Mazar and Cotter, 2007; Hagan et al, 2011); with a well-studied example described for each of these two functions: The TpsB family protein FhaC secretes a partner protein (FHA) through the outer membrane to the extracellular milieu (Mazar and Cotter, 2007; Jacob-Dubuisson et al, 2013). The Omp85/TpsB protein superfamily is characterized through sequence similarity and shared structural characteristics (Yen et al, 2002; Moslavac et al, 2005), there is a clear separation between the Omp family (e.g., BamA) and TpsB family (e.g., FhaC) at the sequence level This is reflected in two defining Pfam profiles: PF01103 (“Bac_surface_Ag”) for Omp proteins and PF03865 (“ShlB”) for TpsB proteins. Despite this distinction, there is an underlying sequence similarity in the membrane-embedded β-barrel domains (Yen et al, 2002; Moslavac et al, 2005), which is represented on a structural level (Clantin et al, 2007; Gruss et al, 2013; Noinaj et al, 2013). In both of these proteins, a series of ∼10 kDa globular domains (Polypeptide Transport Domains or POTRAs; Sanchez-Pulido et al, 2003) stretch out from the N-terminal part of the barrel domain, and are located within the bacterial periplasm
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
